In oil drilling and stimulation activities, a zone of relatively higher permeability may be drilled through or adjacent or in fluid communication with a formation that is to be stimulated. This higher porosity zone can result in effective loss of fluids. During drilling operations, fluid and proppant may be lost to the zone of higher porosity, decreasing pressure in the stimulation zone. This leak-off may result in inadequate well stimulation.
For at least these reasons, higher porosity zones are typically treated with lost circulation or diverting fluids that prevent further leak-off and allow for continued drilling or stimulation. In the case of diverting fluids, especially, it is also desirable that the diverting fluids break down and easily flow back up the well over some period of time. This reduces the overall damage to the formation and maintains maximum oil production levels.
It is also common to encounter areas where unconsolidated sands or formation water are being produced and need to be eliminated. In these situations, a viscous pill is pumped into a targeted area of the wellbore to serve as a barrier to flow. There can be problems associated with these methods, such as high pumping costs and potential slumping of fluid in the wellbore, which may reopen a pathway for flow.
Typical approaches for either lost circulation or diverting fluids are to provide a high fluid viscosity, inclusion of bridging agents in the fluid, such as carbonates, fibers, etc., or a combination of these. Disadvantages of these approaches include:                introduction of bridging materials that increase the probability of formation damage;        increased viscosity that must be overcome by drilling machinery;        higher pumping pressures from high viscosity, particulate laden pills;        potential contamination of other zones in the well; and        required treatment step(s) to later remove the fluids from producing zones.        